Expandable reverse shoulder trial

ABSTRACT

Described herein is an expandable shoulder trial for a reverse shoulder system including a rotatably adjustable insert housed within a humeral cup. The insert has proximal and distal ends, the proximal end having a concave recess therein adapted to receive a glenosphere prosthesis. The distal end of the insert includes a shaft, the shaft having a helical groove disposed on at least a portion thereof. A distal end of the humeral cup is inserted in a humeral stem. The humeral cup has a proximal end including a recess therein, the recess defined by a circular wall. A guide pin protrudes from the circular wall and is adapted to engage the helical groove of the insert shaft. The proximal end of the insert may rotate along an axis toward the proximal end of the humeral cup and along the same axis away from the proximal end of the humeral cup.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 11/974,424, filed on Oct. 12, 2007, the disclosure of which is incorporated herein by reference.

FIELD OF THE TECHNOLOGY

The present invention relates to an expandable reverse shoulder trial for reverse shoulder athroplasty (RSA), and in particular it relates to such a trial including an insert that rotatably engages a humeral cup.

BACKGROUND OF THE INVENTION

The successful outcome of RSA depends greatly on proper soft tissue tension. Since the rotator cuff is either absent or severely compromised and irreparable, the stability of the shoulder joint comes from significant deltoid tension holding the ball and socket joint together.

Existing reverse shoulder systems require a surgeon to pick a trial liner and reduce the shoulder joint with that liner assembled into a humeral cup. If the correct liner is chosen, the soft tissue tension is significant, requiring the surgeon to apply extreme force to the humerus and surrounding soft tissues to reduce the joint. If no additional damage is done during this reduction process, the joint must then be dislocated to allow the surgeon to implant a joint replacement prosthesis.

Dislocation can often be more difficult than reduction and RSA patients often have compromised bone stock and/or soft tissue. The extreme force required to dislocate the joint again may put the patient at risk for other injury and soft tissue trauma. Furthermore, current systems require the surgeon to use a trial and error approach in establishing proper soft tissue tension. This often takes several attempts before adequate stability is achieved.

There currently exists a need for an adjustable trial including an insert that rotatably engages a humeral cup. The insert may first be inserted into the humeral cup and then rotated into a fully collapsed or neutral position. Such a device may allow a surgeon to easily reduce the shoulder joint. Preferably, the insert may then be advanced to a position where optimal deltoid tension is achieved. At this position, the insert and humeral cup are preferably calibrated such that the surgeon may determine a liner thickness corresponding to a dialed position of the insert with respect to the humeral cup. The terms “dialed position” or “dial in” indicate the distance between a proximal end of the insert and a proximal end of the humeral cup. This distance or liner thickness is measured by indications on the insert, such as calibration marks and/or attachment locations in reference to a marker on the humeral cup. This will be further explained in the detailed description.

The surgeon may also perform range of motion (“ROM”) and joint stability analyses during calibration of the trial. Preferably, the surgeon may then easily collapse the trial back to the neutral position and simply dislocate the joint. Further, the trial may also be preferably expanded prior to joint reduction and collapsed prior to joint dislocation repeatedly, depending on surgeon preference. Once the trial has been optimized, a surgeon preferably records the dialed position of the expanded trial. This measurement should preferably be the liner thickness. If this measurement does not correspond to the size of a particular liner in the system, the surgeon may select a next larger sized liner. At this time, the surgeon may remove the trial and then implant a prosthesis including a humeral cup and the selected liner.

SUMMARY OF THE INVENTION

The present invention greatly eases the reduction and dislocation of a shoulder joint during trialing because the surgeon may custom fit a trial to a patient after the joint has been reduced. This will greatly decrease the patient's exposure to intraoperative soft or hard tissue injuries related to extreme forces required to reduce and dislocate the joint. Moreover, the preferred one-step trialing approach of the present invention will also decrease surgical time, which is healthier for the patient and more efficient for the surgeon and hospital. Preferably, the expandable trial also decreases the size and cost of the overall instrument set, since only one trial per glenosphere diameter is generally required.

A main distinguishing characteristic of the adjustable trial from prior art devices is the fact that an insert may be first inserted into a humeral cup and then rotated into a collapsed or neutral position. This preferably allows the surgeon to easily reduce the joint. The trial, including the insert and humeral cup may then be expanded into a second position wherein optimal deltoid tension is preferably achieved. Here, the trial is calibrated such that the surgeon can determine which liner thickness corresponds to the dialed position on the trial.

Following ROM and joint stability analysis, the surgeon can easily collapse the trial back to the neutral position and simply dislocate the joint. The trial may also be expanded prior to joint reduction and collapsed prior to joint dislocation repeatedly, depending on surgeon preference.

The purpose of the present invention is to allow the surgeon to reduce the reverse shoulder trial and surrounding soft tissues into a relaxed state and/or dislocate a reduced shoulder joint while in a relaxed state. This will greatly ease the reduction of the joint. Once reduced, the surgeon may then “dial in” the appropriate liner thickness to achieve proper soft tissue tension. The trial is preferably designed to expand in discreet increments which correspond to liner prostheses that are available in multiple thicknesses. After a liner prosthesis is selected, it is then implanted with a humeral cup prosthesis.

An example of a surgical technique for the expandable reverse shoulder trial of the present invention is as follows:

Step 1: Resect the proximal humerus at a height determined by a typical humeral resection guide and surgical technique. At this point the surgeon may move to glenoid preparation (step 5) or continue with humerus preparation.

Step 2: Prepare the humerus distally in a standard fashion first using intramedullary reamers of increasing size according to surgeon preference.

Step 3: Prepare the proximal humerus using broaches of increasing size. Preferably, starting with a broach that is smaller than the final prosthesis based on preoperative templating.

Step 4: Perform calcar planing to prepare the proximal humerus to ensure proper seating of a humeral cup into the humeral stem and/or perform proximal reaming to create a seat for the cup. A trial humeral cup may also be inserted to assess seating and interference. The cup trial should be removed prior to preparing the glenoid surface.

Step 5: Target the center of the glenoid using the centering guide and drill a centering hole. Insert a guide-wire or guide pin into the centering hole and ream the glenoid face progressively until sub-chondral bone is thoroughly exposed.

Step 6: Place and attach a baseplate on the glenoid face in a desired location.

Step 7: Select an appropriate glenosphere trial and attach to the baseplate.

Step 8: Select an expanding trial including an insert having a recess diameter matching the glenosphere trial diameter. Ensure that the expanding trial is in the fully collapsed or neutral position and insert the trial assembly into a tapered bore in the humeral broach or stem. The joint may now be reduced into a laxed state. Deltoid and remaining cuff tension can then be dialed in by expanding the trial. Laxity, ROM and stability can now be evaluated with the trial components in place. Trialing can also be accomplished by repeatedly reducing the shoulder joint at a specific thickness which the surgeon has dialed in, evaluating the fit and function, collapsing the trial, and dislocating the shoulder.

Step 9: If different components (diameter etc.) are desired, substitutions may be made prior to implanting the prostheses. Once the trial has been optimized, the dialed thickness of the expanded trial is preferably recorded. This measurement preferably will be the thickness of the liner prosthesis.

Step 10: Remove the trial and implant the prostheses.

These steps are an exemplary method of the invention. It is to be understood that modifications can be made to these steps or some of these steps may not be performed without departing from the spirit and scope of the present invention.

As used herein, when referring to bones or other parts of the body, the term “proximal” means closer to the heart and the term “distal” means more distant from the heart. The term “inferior” means lower or bottom and the term “superior” means upper or top. The term “anterior” means towards the front part of the body or the face and the term “posterior” means towards the back of the body. The term “medial” means toward the midline of the body and the term “lateral” means away from the midline of the body.

A first aspect of the present invention is an expandable shoulder trial having an insert including a proximal end and a distal end, the proximal end having a concave recess therein. Preferably, the distal end of the insert includes a shaft, the shaft having a helical groove disposed on at least a portion thereof. Preferably, the trial further includes a humeral cup having a proximal end including a recess therein, the recess defined by a circular wall for securing the insert shaft. A guide pin preferably protrudes from the circular wall into the recess, the guide pin adapted to engage the helical groove of the shaft of the insert. Preferably, the proximal end of the insert may be rotatably adjusted in a first axial direction toward the proximal end of the humeral cup to collapse the trial and alternatively in an opposite second axial direction away from the proximal end of the humeral cup to expand the trial.

In accordance with one embodiment of this first aspect of the present invention, the helical groove of the shaft preferably allows the insert when rotated to move in the first and second axial directions as the insert is rotated in only a first direction (i.e. clockwise or counter-clockwise direction). Preferably, the thickness and/or axial distance between the proximal end of humeral cup and the proximal end of the insert is adjusted by rotating the insert in either the first and or the second directions.

In accordance with yet another embodiment of this first aspect of the present invention, the proximal end of the insert preferably includes an outer face having a plurality of calibration marks arranged thereon.

In accordance with still yet another embodiment of this first aspect of the present invention, the outer face of the insert preferably includes a plurality of attachment locations adapted to engage an adjustment tool for rotating the insert.

In accordance with still yet another embodiment of this first aspect of the present invention, the proximal end of the humeral cup includes a front face having a marker arranged thereon. Preferably, the axial distance between the proximal end of humeral cup and the proximal end of the insert is indicated by the calibration marks on the insert in reference to the marker on the humeral cup.

The trial of the present invention may also be provided as an expandable shoulder trial including a humeral cup having an axis, the humeral cup including a recess defining a substantially circular wall about the axis, the circular wall having a guide portion extending outwardly therefrom. Preferably, the trial further includes an insert having a proximal end and a distal end, the proximal end of the insert having a concave recess disposed thereon, the distal end having a shaft extending therefrom towards the proximal end, the shaft of the insert preferably received in the recess of the cup. Preferably, the shaft includes a helical groove disposed on at least a portion thereof. Preferably, the guide portion is adapted to engage the helical groove of the shaft so that when the insert is rotatably adjusted the insert may move from a neutral position wherein the proximal end of the insert is substantially adjacent to the proximal end of the humeral cup, and into an expanded position wherein the proximal end of the insert is further away from the proximal end of the cup in the axial direction.

A second aspect of the present invention is an expandable shoulder trial including a humeral cup having a distal end portion coupled to a stem, the humeral cup further including a proximal end portion having a base and a circular wall defining a circular recess, the wall having a guide pin protruding therefrom. Preferably the trial further includes an insert having a proximal end portion and a distal end portion for insertion in the circular recess of the humeral cup, the distal end portion having a cam track extending toward the proximal end portion, the cam track adapted to receive the guide pin of the humeral cup. Preferably, the insert is rotatably adjustable along an axis in a first direction such that the distal end portion of the insert moves toward the base of the recess of the humeral cup.

In accordance with one embodiment of this second aspect of the present invention, the insert is rotatably adjustable along the axis in an opposite second direction wherein the distal end of the insert moves away from the base of the recess of the humeral cup.

In one aspect of a method of the present invention, the insert may be rotated in the first direction approximately 60° to reduce the distance between the proximal end of the humeral cup and the proximal end of the insert approximately 2 mm. Preferably, the insert includes an incremental stopping portion every 60° along the guide portion or cam-track of the shaft portion of the insert. As the insert is rotated in either a first or second direction the guide pin of the humeral cup may engage an incremental stopping portion of the insert. This may stop the insert from further rotation until a force great enough to overcome the friction between the guide pin and the incremental stopping portion is produced.

Generally, the present invention is an expandable reverse shoulder trial for RSA. In one aspect of the present invention, the trial is designed to take the place of a kit of trials and to provide the surgeon with greater intraoperative flexibility and ease of trialing during RSA. Prior art devices include trials of increasing thicknesses in “kit” form.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the subject matter of the present invention and the various advantages thereof can be realized by reference to the following detailed description in which reference is made to the accompanying drawings in which:

FIG. 1A is an isometric view of a humeral cup according to an embodiment of the present invention.

FIG. 1B is a front view of the humeral cup according to FIG. 1A.

FIG. 1 c is a side view of the humeral cup according to FIG. 1A.

FIG. 1D is a bottom view of the humeral cup according to FIG. 1A.

FIG. 2A is an isometric view of an alternative embodiment of a humeral cup according to the present invention.

FIG. 2B is a front view of the humeral cup according to FIG. 2A.

FIG. 2C is a side view of the humeral cup according to FIG. 2A.

FIG. 2D is a bottom view of the humeral cup according to FIG. 2A.

FIG. 3A is an isometric view of an insert according to an embodiment of the present invention.

FIG. 3B is a front view of the insert according to FIG. 3A.

FIG. 3C is a side view of the insert according to FIG. 3A.

FIG. 4A is a side view of an alternative embodiment of an insert according to the present invention.

FIG. 4B is a side view of the insert according to FIG. 4A rotated to the left.

FIG. 4C is a detail view A of a section of the insert according to FIG. 4B.

FIG. 5A is an isometric view of an alternative embodiment of an insert of the present invention.

FIG. 5B is a front view of the insert according to FIG. 5A.

FIG. 5C is a side view of the insert according to FIG. 5A.

FIG. 5D is a side view of the insert similar to FIG. 5C but rotated to the left.

FIG. 6A is a side view of an alternative embodiment of an insert according to the present invention.

FIG. 6B is a side view of the insert according to FIG. 6A rotated to the left.

FIG. 7A is an isometric view of an adjustment tool according to an embodiment of the present invention.

FIG. 7B is a front view of the adjustment tool according to FIG. 7A rotated 180°.

FIG. 7C is a side view of the adjustment tool according to FIG. 7A from the left side.

FIG. 8 shows an axis of the humeral cup of FIG. 2A aligned with an axis of the insert of FIG. 5A prior to assembly.

FIG. 9A is an assembled view of the humeral cup of FIG. 1A and the insert of FIG. 3A in a fully collapsed or neutral position.

FIG. 9B is an assembled isometric view of the humeral cup and insert of FIG. 9A assembled to an exemplary humeral stem.

FIG. 9C is an assembled front view of the humeral cup, insert, and humeral stem according to FIG. 9B.

FIG. 9D is an assembled side view of the humeral cup, insert, and humeral stem according to FIG. 9C.

FIG. 10A is an assembled view of the humeral cup of FIG. 1A and the insert of FIG. 3A in an expanded position.

FIG. 10B is an assembled isometric view of the humeral cup and insert of FIG. 10A assembled to an exemplary humeral stem.

FIG. 10C is an assembled front view of the humeral cup, insert, and humeral stem according to FIG. 10B.

FIG. 10D is an assembled side view of the humeral cup, insert, and humeral stem according to FIG. 10C.

FIG. 11A is an assembled view of the humeral cup of FIG. 2A and the insert of FIG. 3A in a fully collapsed or neutral position.

FIG. 11B is an assembled front view of the humeral cup and insert of FIG. 11A assembled to an exemplary humeral stem.

FIG. 11C is an assembled side view of the humeral cup, insert, and humeral stem according to FIG. 11B.

FIG. 12A is an assembled view of the humeral cup of FIG. 2A and the insert of FIG. 3A in an expanded position.

FIG. 12B is an assembled front view of the humeral cup and insert of FIG. 12A assembled to an exemplary humeral stem.

FIG. 12C is an assembled side view of the humeral cup, insert, and humeral stem according to FIG. 12B.

FIG. 13A is an assembled view of the humeral cup of FIG. 2A and the insert of FIG. 5A in a fully collapsed or neutral position.

FIG. 13B is an assembled front view of the humeral cup and insert of FIG. 13A assembled to an exemplary humeral stem.

FIG. 13C is an assembled side view of the humeral cup, insert, and humeral stem according to FIG. 13B.

FIG. 14A is an assembled view of the humeral cup of FIG. 2A and the insert of FIG. 5A in an expanded position.

FIG. 14B is an assembled front view of the humeral cup and insert of FIG. 14A assembled to an exemplary humeral stem.

FIG. 14C is an assembled side view of the humeral cup, insert, and humeral stem according to FIG. 14B.

DETAILED DESCRIPTION

Referring to FIGS. 1A-1D, there is shown an embodiment of a humeral cup of the present invention designated generally by reference numeral 10. As shown in those figures, cup 10 includes a proximal end 12 and a distal end 14. Cup 10 preferably further includes a circular wall 16 and a base 18 defining a recess 20. Recess 20 defines a central axis 22 as shown in FIG. 1C. Preferably, a guide portion 23 protrudes from wall 16. Guide portion 23 is preferably configured as a pin.

In the preferred embodiment, proximal end 12 and distal end 14 of cup 10 are not coplanar. Between distal end surface 14 and proximal end surface 12 is a hemispherical outer surface 24. In an alternative embodiment, as shown in FIGS. 2A-2D, a cup 10′ further includes a concave surface 26 located between a proximal end surface 12′ and a distal end surface 14′. Surface 26 faces medially and is preferably configured to allow for greater articulation of cup 10′ with respect to a scapula bone after cup 10′ has been trialed in the body. Cups 10 and 10′ generally include all of the same features except for cup 10′ including concave surface 26 and a partially hemispherical outer surface 24′.

As shown in FIGS. 2A-2 d, surface 26 may include a bore 28′ associated therewith. Bore 28′ may initially extend from surface 26 through wall 16′ into recess 20′. Generally, bore 28′ is configured to receive the guide pin 23′ therein. Preferably, guide pin 23′ has an end which protrudes outwardly from wall 16′ into recess 20′. After guide pin 23′ is located in position, such as shown generally in FIGS. 2A-2C, bore 28′ may be filled such that surface 26 is a curved flat surface throughout.

Preferably, distal end 14, 14′ of cup 10, 10′ includes a trunion 30, 30′ protruding distally therefrom. Trunion 30 is preferably configured to mate with a corresponding bore in a proximal end of a humeral stem 80 as shown for example in FIGS. 9A-9D. Preferably, trunion 30, 30′ has a male taper that may easily be secured to the corresponding tapered bore of humeral stem 80. Other quick-connect mechanisms known in the art may be used to connect cup 10, 10′ to a humeral stem, for example, threaded connections, other pressure-fit connections, and clasps.

Proximal end 12, 12′ of cup 10, 10′ preferably has a substantially flat proximal surface portion 32, 32′. Preferably, proximal surface portion 32, 32′ includes a central rounded edge 34, 34′ which blends with wall 16, 16′ and has a rounded edge 36, 36′ which blends with outer surface 24, 24′.

Preferably, surface 32, 32′ of humeral cup 10, 10′ includes a marker 38, 38′ arranged thereon. Marker 38, 38′ is preferably of any configuration that gives a user, such as a surgeon or other operating room personnel, a visual frame of reference for the position of an insert with respect to humeral cup 10, 10′.

Referring to FIGS. 3A-3C, there is shown a first embodiment of the insert of the present invention designated generally by reference numeral 40. Preferably, insert 40 includes a proximal end portion 42 and a distal end 44 portion, the proximal end portion 42 having a proximal surface 52 including a proximally facing concave recessed surface 46 therein. Preferably, distal end portion 44 of insert 40 includes a shaft 48, the shaft having a helical groove 50 disposed on at least a portion thereof. Guide pin 23, 23′ protruding from circular wall 16, 16′ into recess 20, 20′ is configured to engage helical groove 50 of shaft 48 such that while guide pin 23, 23′ is engaged with helical groove 50 at least a portion of shaft 48 is located within recess 20, 20′.

As shown in FIGS. 4A and 4B, an alternative embodiment of insert 40 may include a plurality of incremental stopping features or indents 51 along groove 50. In a preferred embodiment, each indent 51 is located approximately every 60° along groove 50. As insert 40 having indents 51 is rotated in a first or second direction D1, D2, guide pin 23, 23′ of cup 10, 10′ may engage an indent 51 of insert 40. Indent 51 is configured to stop insert 40 from further rotation until a force great enough to overcome the friction between guide pin 23, 23′ and indent 51 is produced.

Preferably, insert 40 may be rotatably adjusted about axis 22 by rotating in a first direction D1 as generally depicted on FIG. 3A, such that insert 40 may move into recess 20, 20′ of humeral cup 10, 10′. Alternatively, insert 40 may be rotatably adjusted about axis 22 in an opposite second direction D2, such that insert 40 may move out of recess 20, 20′ of humeral cup 10, 10′. Preferably, the axial distance between proximal end 12, 12′ of humeral cup 10, 10′ and proximal surface 52 of proximal end portion 42 of insert 40 is adjusted along axis 22 by rotating insert 40 in either first and/or second directions D1, D2.

As shown in FIG. 3A, proximal end surface 52 preferably includes a plurality of calibration marks 54 arranged thereon. Preferably, proximal end portion 42 of insert 40 further includes a plurality of alternating convex and concave side faces, 56 and 58 respectively. As shown in FIG. 3A, calibration marks 54 may extend from proximal surface 52 onto side faces 56, 58. Side faces 56, 58 may further include a plurality of attachment locations 60 therein. Preferably, attachment locations 60 are adapted to receive an adjustment tool 61 shown generally in FIGS. 7A-7C. A surgeon or any other operating room personnel may use adjustment tool to rotate insert 40 along axis 22 in either the first and/or second directions D1, D2.

Preferably, adjustment tool 61 includes a handle portion 62 having a shaft 64 protruding therefrom, the shaft having a tip 66 protruding therefrom. Handle portion 62 may further include a knurled portion 68 for easy gripping. It is contemplated by the present invention that tool 61 may have many alternative configurations. Tool 61 is an exemplary instrument for easily rotating insert 40 along axis 22 in either the first and/or second directions D1, D2.

As stated above, calibration marks 54 of insert 40 may also be arranged on side faces 56, 58. Preferably, the axial distance between proximal end 12, 12′ of humeral cup 10, 10′ and surface 52 of proximal end portion 42 of insert 40 is measured by calibration marks 54 on any of surfaces 52, 56, and 58 of insert 40 in reference to marker 38, 38′ of humeral cup 10, 10′.

For example, marker 38, 38′ of humeral cup 10, 10′ may be lined up with one of the calibration marks 54 of insert 40. Preferably, insert 40 may then be rotated in direction D1 approximately 60° to reduce the distance between proximal end 12, 12′ of humeral cup 10, 10′ and proximal end surface 52 of insert 40 approximately 2 mm. Insert 40 may then be rotated another 60° in direction D1 until a second calibration mark 54 to the left of the calibration mark 54 is now instead lined up with marker 38, 38′ of humeral cup 10, 10′. In this case, the distance between proximal end 12, 12′ of humeral cup 10, 10′ and proximal end surface 52 of insert 40 would be further reduced approximately 2 mm for a total of 4 mm.

One skilled in the art would understand that the distance between calibration marks may be less than or greater than 60° apart. Preferably, calibration marks are between 30° and 120° apart. More preferably, calibration marks are between 30° and 60° apart. Further, one skilled in the art would understand that the pitch of groove 50 determines the distance that insert 40 collapses or expands between calibration marks. Preferably, the distance between proximal end 12, 12′ of humeral cup 10, 10′ and proximal end surface 52 of insert 40 may be reduced or expanded 0.5 mm to 4 mm between calibration marks 54. Further, an exact number of calibration marks 54 would not be needed to indicate a distance X that insert 40 may travel in moving from the fully collapsed or neutral position as shown for example in FIGS. 9A-9D, to an expanded position, shown generally in FIGS. 10A-10D. For example, if the surgeon determines that proper deltoid tension has occurred after expanding the trial approximately 11 mm, attachment locations 60 may be located between calibration marks 54. In this case, the surgeon may approximate the distance insert 40 has collapsed or expanded.

In the preferred embodiment, insert 40 may collapse and/or expand between 0 and 12 mm. More preferably, insert 40 may collapse or expand 6 mm. It is contemplated in the present invention that more or less than six calibration marks 54 may be arranged on insert 40.

Preferably, as shown in FIGS. 11A-11C, a concave side face 58 of insert 40 is configured to align with surface 26 of humeral cup 10′. It is within the scope of the present invention for one of convex surfaces 56 of insert 40 to be located adjacent to bottom surface 26 as well.

An alternative embodiment of insert 40 of the present invention is designated generally by reference numeral 40′ as shown in FIGS. 5A-5D. Preferably, insert 40′ includes a proximal end portion 42′ and a distal end portion 44′, the proximal end portion 42′ having a proximal surface 52′ including a proximally facing concave recessed surface 46′ therein. Preferably, distal end portion 44′ of insert 40′ includes a shaft 48′ having a helical groove 50′ disposed on at least a portion thereof. Guide pin 23, 23′ protruding from circular wall 16, 16′ into recess 20, 20′ is configured to engage helical groove 50′ of shaft 48′ such that while guide pin 23, 23′ is engaged with helical groove 50′ at least a portion of shaft 48′ is located within recess 20, 20′.

As shown in FIGS. 6A and 6B, an alternative embodiment of insert 40′ may include a plurality of incremental stopping features or indents 51′ along groove 50′. In a preferred embodiment, each indent 51′ is located approximately every 60° along groove 50′. As insert 40′ having indents 51′ is rotated in a first or second direction D1, D2, guide pin 23, 23′ of cup 10, 10′ may engage an indent 51′ of insert 40′. Indent 51′ is configured to stop insert 40′ from further rotation until a force great enough to overcome the friction between guide pin 23, 23′ and indent 51′ is produced.

Referring to FIGS. 5A-5D, helical groove 50′ of shaft 48′ of insert 40′ preferably allows proximal end portion 42′ of insert 40′ to move away from proximal end 12, 12′ of humeral cup 10, 10′ and thereafter toward proximal end 12, 12′ of humeral cup 10, 10′ as insert 40′ is rotated in only the first direction D1. For example, if insert 40′ is in the fully collapsed or neutral position as shown in FIGS. 13A-13C, generally defined by shaft 48′ of insert 40′ being fully seated in recess 20, 20′ a surgeon or other operating room personnel may rotate insert 40′ in first direction D1. This rotation will cause shaft 48′ of insert 40′ to move out of recess 20, 20′ wherein proximal end portion 42′ will thus move away from proximal end 12, 12′ of humeral cup 10, 10′. Eventually, the trial will be in a fully expanded position, shown generally in FIGS. 14A-14C. This is generally the point where an outer surface 52′ of proximal end portion 42′ is furthest away from proximal end 12, 12′ while insert 40′ is still assembled or engaged to humeral cup 10, 10′. Because of the configuration of helical groove 50′, if insert 40′ continues to rotate in first direction D1, proximal end portion 42′ will begin to start moving back towards proximal end 12, 12′ of humeral cup 10, 10′.

Preferably, proximal surface 52′ includes a plurality of calibration marks 54′ arranged thereon. Preferably, proximal end portion 42′ of insert 40′ further includes a plurality of alternating convex and concave side faces, 56′ and 58′ respectively. Side faces 56′, 58′ may further include a plurality of attachment locations 60′ therein. Preferably, attachment locations 60′ are adapted to receive a portion of adjustment tool 61. A surgeon or any other operating room personnel may use adjustment tool 61 to rotate insert 40′ along axis 22′ in either the first and/or second directions D1, D2.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. For example, the present invention may be applied to hip systems as well. 

The invention claimed is:
 1. A reverse shoulder system comprising: at least one stem member having a shaft portion adapted to be received in a canal of a humeral bone of a patient; a trial cup and a prosthesis cup each adapted to be coupled at a distal end thereof to the at least one stem member, the trial cup and prosthesis cup each having a proximal end surface including a recess therein; a trial insert and a prosthesis insert each including a proximal end surface and a shaft portion having a distal end, the shaft portion of the trial insert and prosthesis insert each adapted to be received in the recess of the trial cup and prosthesis cup, respectively, wherein a linear trial distance is measured between the proximal end surface of the trial cup and the proximal end surface of the trial insert when at least a portion of the trial insert is coupled to the trial cup and is linearly adjusted into a desired position during trialing, and wherein a linear prosthesis distance is measured between the proximal end surface of the prosthesis cup and the proximal end surface of the prosthesis insert when the prosthesis insert is coupled to the prosthesis cup, and wherein the linear trial distance is substantially the same as the linear prosthesis distance.
 2. The reverse shoulder system of claim 1, wherein the at least one stem member is a broach.
 3. The reverse shoulder system of claim 1, wherein the at least one stem member is a humeral implant.
 4. The reverse shoulder system of claim 1, wherein the at least one stem member is a broach and a humeral implant.
 5. The reverse shoulder system of claim 1, wherein the at least one stem member has a proximal end including an engagement member and the distal end portion of both the trial cup and prosthesis cup include an engagement member configured to engage to the engagement member of the at least one stem member in order to couple either the at least one stem member and trial cup or at least one stem member and prosthesis cup.
 6. The reverse shoulder system of claim 1, wherein the recess of the trial cup is defined by a circular wall, the circular wall having a guide pin protruding from the circular wall into the recess, the guide pin adapted to engage a helical groove of the shaft portion of the trial insert, such that the proximal end surface of the trial insert may be linearly adjusted by rotating the trial insert in a first direction along a longitudinal axis of the trial cup toward the proximal end surface of the trial cup and in an opposite direction along the longitudinal axis of the trial cup away from the proximal end surface of the trial cup by the interaction of the guide pin and the groove.
 7. The reverse shoulder system of claim 1, wherein the proximal end surface of both the trial insert and prosthesis insert have a concave recess portion.
 8. The reverse shoulder system of claim 1, wherein dimensions of the prosthesis cup are substantially the same as dimensions of the trial cup such that the prosthesis cup and trial cup are substantially a same size.
 9. The expandable shoulder trial of claim 1, wherein an outer face of the trial insert adjacent the proximal end surface thereof includes a plurality of attachment locations adapted to be engaged by an adjustment tool.
 10. A reverse shoulder system comprising: at least one stem member having a shaft portion adapted to be received in a canal of a humeral bone of a patient; a trial cup and a prosthesis cup each adapted to be coupled at a distal end thereof to the at least one stem member, the trial cup and prosthesis cup each having a proximal end surface including a recess therein, the recess termination at a distal end surface; a trial insert and a prosthesis insert each including a proximal end surface and a shaft portion having a distal end, the shaft portion of the trial insert and prosthesis insert each adapted to be received in the recess of the trial cup and prosthesis cup, respectively, wherein a linear trial distance is measured between the distal end surface of the recess of the trial cup and the proximal end surface of the trial insert when at least a portion of the trial insert is coupled to the trial cup and is linearly adjusted into a desired position during trialing, and wherein a linear prosthesis distance is measured between the distal end surface of the recess of the prosthesis cup and the proximal end surface of the prosthesis insert when the prosthesis insert is coupled to the prosthesis cup, and wherein the linear trial distance is substantially the same as the linear prosthesis distance.
 11. The reverse shoulder system of claim 10, wherein the at least one stem member is a broach.
 12. The reverse shoulder system of claim 10, wherein the at least one stem member is a humeral implant.
 13. The reverse shoulder system of claim 10, wherein the at least one stem member is a broach and a humeral implant.
 14. The reverse shoulder system of claim 10, wherein the at least one stem member has a proximal end including an engagement member and the distal end portion of both the trial cup and prosthesis cup include an engagement member configured to engage to the engagement member of the at least one stem member in order to couple either the at least one stem member and trial cup or at least one stem member and prosthesis cup.
 15. The reverse shoulder system of claim 10, wherein the recess of the trial cup is defined by a circular wall, the circular wall having a guide pin protruding from the circular wall into the recess, the guide pin adapted to engage a helical groove of the shaft portion of the trial insert, such that the proximal end surface of the trial insert may be linearly adjusted by rotating the trial insert in a first direction along a longitudinal axis of the trial cup toward the proximal end surface of the trial cup and in an opposite direction along the longitudinal axis of the trial cup away from the proximal end surface of the trial cup by the interaction of the guide pin and the groove.
 16. The reverse shoulder system of claim 10, wherein the proximal end surface of both the trial insert and prosthesis insert have a concave recess portion.
 17. The reverse shoulder system of claim 10, wherein dimensions of the prosthesis cup are substantially the same as dimensions of the trial cup such that the prosthesis cup and trial cup are substantially a same size.
 18. The expandable shoulder trial of claim 10, wherein an outer face of the trial insert adjacent the proximal end surface thereof includes a plurality of attachment locations adapted to be engaged by an adjustment tool.
 19. A method of determining proper deltoid tension using a reverse shoulder system comprising: inserting a shaft portion of a stem member in a canal of a humeral bone of a patient; coupling a cup member at a distal end thereof to the stem member, the cup member having a proximal end surface including a recess therein; inserting at least a portion of a shaft portion of a trial insert into the recess of the cup member; moving the shaft portion of the trial insert within the recess of the trial cup until proper deltoid tension is achieved; measuring a linear trial distance between the proximal end surface of the cup member and a proximal end surface of the trial insert upon achieving proper deltoid tension; and removing the trial insert from the cup member and inserting at least a portion of a shaft portion of a prosthesis insert into the recess of the cup member such that a linear prosthesis distance measured between the proximal end surface of the cup member and a proximal end surface of the prosthesis insert is substantially the same as the linear trial distance.
 20. A method of determining proper deltoid tension using a reverse shoulder system comprising: inserting a shaft portion of a stem member in a canal of a humeral bone of a patient; coupling a trial cup at a distal end thereof to the stem member, the trial cup having a proximal end surface including a recess therein; inserting at least a portion of a shaft portion of a trial insert into the recess of the trial cup; moving the shaft portion of the trial insert within the recess of the trial cup until proper deltoid tension is achieved; measuring a linear trial distance between the proximal end surface of the trial cup and a proximal end surface of the trial insert upon achieving proper deltoid tension; uncoupling the trial cup from the stem member and coupling a prosthesis cup to the stem member, the prosthesis cup having a proximal end surface including a recess therein; and inserting at least a portion of a shaft portion of a prosthesis insert into the recess of the prosthesis cup such that a linear prosthesis distance measured between the proximal end surface of the prosthesis cup and a proximal end surface of the prosthesis insert is substantially the same as the linear trial distance. 